Costa Rica discovers new crab species

December 3, 2010

A group of Costa Rican biologists has discovered a new species of river crab, and experts believe the crab exists only in the country’s Southern Zone.

The discovery of Allacanthos yawi was published in the September 2010 edition of the zoological taxonomist journal Zootaxa.

The new species was found at 1,000 meters above sea level, along the banks of the Río Volcán and in the Río Grande de Térraba basin. The crabs were also found along the Cañas River.

The male crab measures 2.8 centimeters in width and 1.6 cm in length, and the female can grow to 2.7 cm wide.

They are distinguished by olive and green colors on their backsides, and yellow and turquoise shades on their bellies.

Costa Rica has 18 species of river crabs representing six different genera, including the most recent discovery.

For Ingo Wehrtmann, a University of Costa Rica Zoology Museum researcher who helped identify the crustacean, the discovery is a rare treat.

“To discover a new species of river crab for the country isn’t something that happens often,” he said.

The crab was originally found in 2009 by Luis Rólier Lara, a biologist working near the Southern Zone’s Buenos Aires. Lara was conducting research for the Costa Rican Electricity Institute’s proposed El Diquís hydroelectric plant.

The dam, should it be built, would be the largest hydroelectric project in Central America, producing up to 630 megawatts.

After discovering the crab, Wehrtmann pushed for its protection, warning that expansion of nearby pineapple farms could threaten the crab’s habitat.

“This discovery should motivate us to protect the rivers, streams and habitats that shelter a large number of aquatic insect species, fish and now crabs that are unique to Costa Rica and are being threatened by pollution,” he said.

Brazilian crab expert Célio Magalhaes described the new species for Zootaxa, and its name was chosen with help from Costa Rican archaeologist Melania Pérez.

Yawi means “river crab that lives under rocks” in Cabécar, an indigenous language from the region.

Scientists based the identification of the new species on the male’s gonopod, or external reproductive appendage.

According to the paper published in Zootaxa, the Allacanthos yawi male is the first known river crab with a gonopod that has a “narrowing distal part.” By comparison, other types of Allaconthos river crab have straight gonopods.

Research on and identification of Allacanthos yawi was funded by Brazil’s National Board of Scientific and Technological Development and by Costa Rica’s National  Board of Scientific and Technological Research.

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